Dynamic impacting machine



May 29, 1952 J. B. oTTEsTAD ETAL 3,036,538

DYNAMIC IMPACTING MACHINE Filed Sept. 24, 1958 C5 Sheets-Sheet 1 Q w M Mm N Q z l NPM A s* g i iii" `1 f k1 ||[1 wm: 15 |H| m SX $9 "i @n "QQ E1 s l MI u' W i lll May 29, 1962 J. B. oTTEsTAD ETAL 3,036,538

DYNAMIC IMPACTING MACHINE 3 Sheets-Sheet 2 Filed Sept. 24. 1958 o. lsSHw EBM www. a4@ L@ ZW as@ mam),

fMRI/Ey May 29, 1962 J. B. oTTEsTAD ETAL 3,036,538

DYNAMIC IMPACTING MACHINE Filed Sept. 24, 1958 3 Sheets-5h98?l 3 rramdqy3,036,538 DYNAMIC lMPACTIN G MACHINE Jack B. Otte-stad, Claremont,Samuel A. Sheen, West Covina, and Edward W. Baker, Pomona, Calif.,assignors to General Dynamics Corporation, San Diego, Calif., acorporation of Delaware Filed Sept. 24, 1958, Ser. No. 763,002 8 Claims.(Cl. 113-45) This invention relates generally to a dynamic impact-V ingapparatus; more particularly, it relates to a dynamic impactingapparatus for providing high impact energy with relatively lowfoundation loading.

High energy rate devices of the prior art, for use in such applicationsas sheet metal forming, have generally been characterized by certainshortcomings and disadvantages, such as requiring relatively massivefoundations. Among these devices are dead-weight machines, drop towers,devices utilizing explosive charges, and devices for transmitting highlevel energy to hydraulic systems. These devices have generally requiredlarge apparatus and/ or large foundations. The devices have generallynot provided relatively accurate control of the rate of energyapplication. Some have not provided sufficiently high energy potentials.Further, use of certain of the devices has involved danger to personnel.

The present invention provides an apparatus wherein the acceleratingaction of an impacting member causes a movably mounted reaction assemblyto be reactively accelerated in the opposite direction at relatively lowacceleration. The impact member is accelerated by an actuator on thereaction assembly and impacts a workpiece on the reaction assembly. Thepresent invention utilizes dynamic force systems within the apparatusitself for dynamically absorbing energy of acceleration and impact. Therelatively large mass of the movably mounted reaction assembly is animportant factor in preventing transmission of energy to the foundation,because the mass resists acceleration and movement of the reactionassembly. A large proportion of the impact energy is available foruseful work. The preferred embodiment of the invention herein shown anddescribed utilizes an actuator of the type described and claimed in thecopending application of Jack B. Ottestad, Serial No. 617,0114, filedOctober 19, 1956, now Patent No. 2,979,938 and in the copendingapplication of Jack B. Ottestad and Samuel Arthur Skeen, Serial No.683,855, filed September 13, 1957, now Patent No. 2,949,096.

In the embodiment herein shown and described, shock absorber assembliesare provided to assist in restricting acceleration and movement of thereaction assembly in reaction to acceleration of the impact member andin response to the impact of that member on the reaction assembly. Theshock absorbers thus reduce transmission of forces to the foundation. Inthe preferred embodiment, the reaction assembly and the impact memberare moving in opposite directions at the time of impact, thus increasingthe proportion of energy transmitted to the workpiece and decreasing theproportion of energy transmitted to the foundation. After impact, theimpact lmember and reaction assembly are decelerated by dynamic forcesystems in the apparatus, including a decelerating force developed by acushion plunger in the actuator.

The apparatus of the present invention produces high impact energy withrelatively low foundation loading. It therefore obviates the necessityfor massive foundations, because only a relatively small proportion ofimpact energy is transmitted to the foundation. It provides means fortransmitting high impact energy at high rates with a relatively smallapparatus. Utilization of the actuator shown and described in thecopending applications hereite rates tent 3,036,538 Patented May 29,1962 inabove mentioned provides means for accurately controlling therate of energy application. Use of the present invention involvesrelatively little danger to operating personnel.

It is therefore an object of the present invention to provide anapparatus for producing impact energy with relatively low foundationloading.

An object of this invention is the provision of an impacting apparatuswherein the inertia of a movable reaction assembly results in thetransmission of only a relatively small proportion of impact energy to afoundation.

lt is an object of this invention to provide an impacting machine whichprovides high efficiency by utilizing a high proportion of energy foruseful work While transmitting a low proportion of energy to afoundation.

An object of the present invention is the provision of an impactingapparatus wherein a large proportion of the energy developed is absorbeddynamically by force systems in the apparatus with relatively littletransmission of energy to a foundation.

An object of this invention is the provision of a relatively smallself-contained apparatus for the rapid transmission of high level impactenergy.

An object of the present invention is to provide high impact energythrough the impact of oppositely accelerated masses with relativelylittle transmission of energy to a foundation.

It is another object of this invention to provide an impacting machinewherein an impact member is accelerated to impinge on a movable reaction`assembly which has been accelerated in the opposite direction inreaction to the acceleration of the impact member.

Another object of the present invention is the provision of an impactingmachine capable of high rate application of high level energy with ahigh degree of safety to personnel.

It is another object of this invention to provide an impacting machinecapable of energy transmission to a workpiece at a high controlled rate.

Other objects and features of the present invention, as Well as manyadvantages thereof, will become apparent to those skilled in the artfrom a consideration of the following description, the appended claimsand the accompanying drawings, wherein:

FIGURE 1 is an elevational view of an impacting machine according to thepresent invention;

FIGURE 2 is an enlarged elevational view, partially in section, of theimpacting Vmachine of FIGURE 1;

FIGURE 3 is `an elevational View taken at line 3 3 of FIGURE 2;

FIGURE 4 is an elevational sectional View taken at line l-ri of FIGURE2;

FIGURE 5 is an enlarged view, partially in section, showing details ofthe shock absorber assembly utilized with the present invention; and

FIGURES 6, 7, 8 and 9 are elevational views. partially in section,showing the impacting machine of FIGURES 1 and 2 at diiferent stages ofits operation.

Referring to the drawings, and particularly to FIG- URES l and 2, apreferred embodiment of the dynamic reaction apparatus of the presentinvention is shown as including a frame structure 10 slidably mounted ina foundation formed by foot assemblies 12. The frame structure includesthree guide rods 14, 16 and 18 secured to an end member 26 by nuts 22.and by lock rings 24. Nuts 28 secure a bolster 26 on the guide rods, andlock sleeves 3i) provide for adjustment of the axial position of thebolster on the rods.

Guide rods 16 and 13 are slidable in bearings 32 in foot assemblies 12,as illustrated in FIGURES 1 and 5, to slidably mount the frame structure10 on the foundation.

Disposed about each of guide rods 16 and 18 is a shock absorber assembly34 which extends between the two foot assemblies supporting eachrespective guide bar as shown in FIGURE 5. Each of the assembliesincludes two cylindrical sections 36 and 38, which are secured inclamped relation with an orifice ring 4o by end caps 42 and 44. The endcaps are provided with seal rings in appropriate grooves to providepressure sealing between the cylindrical sections and the guide rod. Theorifice ring has a plurality of small axially extending orifices, asshown, and is provided with appropriate seal rings for pressure sealing.

An annular piston 46 is secured to the guide rod between a pair of splitlock rings 50 and piston 43 is similarly secured. The annular pistonsare provided with seal rings in appropriate grooves for pressure sealingbetween the cylindrical housing and the guide rod.

From the foregoing and from FIGURE 5, it will be observed that a coaxialpressure chamber 52 is defined between the orifice ring and annularpiston 46, and that a similar chamber 54 is defined between the orificering and annular piston 48. It will be observed that a coaxial pressurechamber 56 is defined between annular piston 46 and end cap 42, and thata chamber 5S is provided between the annular piston 48 and end cap 44.Chambers S2 and 54 are filled with oil through openings 60 and 62,respectively, in which appropriate filler plugs are threaded. Apneumatic valve 64 is provided for the provision and maintenance of airpressure .in chambers 56 and 58.

The frame structure and an actuator housing 66 together constitute a`reaction assembly. The actuator housing is slidably mounted on the guiderods by bearings 68 disposed in appropriate openings in end walls 70 and72 Of the housing. As illustrated in FIGURES 2 and 4, the actuator endwalls are provided with circularly arranged openings for accommodating-tie bolts 74. Cylindrical sections 76 and 78, an orifice plate or wall79 and end fitting plates Si) and 82 are secured in clamped relationwith the end walls by the tie bolts. Pressure sealing for the actuatorhousing is provided by resilient seal rings in appropriate grooves inthe fitting plates and in the orifice wall member. An orifice 84 isprovided in the orifice plate for a purpose which is hereinafterexplained.

The cylindrical actuator housing may be considered as divided intopressure chambers 86 and 88 by the orifice plate. A passage 90 in theorifice plate interconnects chamber 86 with a source of pressure (notshown). The orifice plate has a passage 91 therein. A passage 92,extending through fitting plate 82 and end wall 72, is provided with anappropriate fluid coupling which interconnects chamber 88 with a sourceof pressure (not shown). A .coupling 93 in a similar passage is for thepurpose of adding or removing oil.

An actuator piston 94 is positioned in chamber 88. A circular seal base96 is secured by a bolt in an appropriate recess in the face of thepiston and is provided with a groove in which a circular resilientpressure seal 9S is secured by bonding. As shown, circular seal 9S isadapted to encircle orifice 84 when the actuator piston is seatedagainst the orifice plate. An annular sealing element 100 in aperipheral groove in the piston provides pressure sealing between thepiston and cylindrical section 78. Bearing rings 102 are disposed onboth sides of the sealing element in recesses in the piston periphery toreduce sliding friction and to maintain alignment between the piston andthe cylindrical section. A reduced end portion of an impact member orthrust column 104 is secured in an opening in the piston. The thrustcolumn extends through aligned openings in fitting plate 82 and end wall72, and is slidably received in a bearing disposed opening 106 of theend wall. A seal ring in a groove within this opening provides pressuresealing.

A die element 107 at the end of the impact member M4 confronts acooperating die member 108 on anvil lit), which is secured to bolster 26in confronting relation with the thrust column. A workpiece 112 ispositioned to be impacted between the thrust column and the die member,as shown in FIGURE 2.

A cushion plunger 114 is positioned in chamber 36 and carries aperipheral annular seal M6 and bearing rings in appropriate recesses.These are similar to the seal and bearing rings associated with theactuator piston. The plunger has an opening for securing a threadedportion of a connecting bar 118, which is slidably received in a bearing12)` in an axial opening in end wall '70. A bolt 122 and a retainingdisc assist in securing the plunger to the bar. The connecting bar issecured to end member 26' by bolts 124, which extend through circularlyspaced openings in a flange portion of the bar. A helical spring T126 isretained between the head of each bolt and flange portion, so that theend member and the entire frame structure if) may move relative to theconnecting bar and shock piston against the resilient urging of thesprings, when the cushion plunger seats against end fitting plate 80.

From the foregoing description, it will be understood that the impactingmachine includes three structures, each olf which is movable relative tothe others land relative to a foundation. The frame structure 16 isslidably mounted in bearings on the foundation. As described above, theactuator housing is slidably mounted on the frame structure, these twostructures forming the reaction assembly. The actuator piston and thrustcolumn are movable relative to the actuator housing.

The actuator is adapted to impart high acceleration to the impact memberor thrust ycolumn 104. The operation of the actuator is Idescribed inthe copending applications hercinbefore identified. it is brieflydescribed herein for convenience of reference to the present invention.A setting pressure is first introduced into chamber 8g through passage92. This pressure acts upon the thrust column side of piston 94 andurges the piston against orifice plate 7 9. This compresses circularresilient seal against the surface of the orifice plate to effect apositive pressure seal which isolates chamber 8S from chamber S6. Asecond and higher pressure is established in chamber 66 through passage90 in the `orifice plate. This actuating pressure acts upon the area ofseal plate 96 within seal 98 and is predetermined to balance the `forceexerted by the setting pressure upon the larger area on the oppositeside of the piston.

To trigger the actuator, the pressure in chamber 86 is increased by apressure differential sufficient to unbalance the forces upon theactuator piston and cause movement of the piston from the orifice plate.Circular seal 9S is thus disengaged and the high actuating pressure isreleased substantially instantaneously upon the area of piston 94outside circular seedL 9S. A great net force is thus suddenly applied tothe piston and impels it from the orifice plate with extremely highacceleration'. As explained in the copending applications hereinbeforementioned, the force and acceleration of the piston and the thrustcolumn 164 are functions of the pressures in chambers 86 and 88, thepiston and thrust column masses, and the ratio between the piston areasupon which the pressures act.

The operation of the impacting machine of the present invention isillustrated in FIGURES 6 through 9. The rapid rightward racceleratingaction `of piston 94 causes a leftward reaction on the reactionassembly. From the geometric relations of the parts, as shown in FlGURES2 and 7, it will be observed and understood that the forces exertedwithin the housing by the actuating pressure become unbalanced uponrightward movement of the piston from the orifice plate. In effect, theforces on the orifice plate become balanced and an accelerating force isexerted leftward on the cushion plunger 114. This force is transmittedto the actuator housing `and to the frame structure, which are therebyaccelerated leftward simultaneously, with the rapid rightwardacceleration of the thrust column, as indicated in FIGURE 7.

The mass of the frame structure l and the housing being large relativeto the mass of the actuator piston and thrust column, its high inertiarestricts its movement and acceleration. Therefore, relatively lowacceleration is imparted to the movable frame and housing in comparisonwith the high acceleration of the thrust column and actuator piston, andthe heavy frame and housing absorb a considerable portion of thereaction energy in accelerating without transmitting the energy to thefoundation.

Leftward movement of the reaction assembly is also resisted -by theshock absorbers 34, which decelerate the frame structure l@ by forcingoil through the restricted orifices in orifice ring 4b, in Aa mannerwell known in the art. Although these idecele-rating means assist inrestricting movement `and acceleration of the reaction assembly, it isto be understood that the apparatus of the present invention may bedesigned to function without shock absorbers. rThe relation between theinertias of the reaction assembly mass and the mass of the piston andthrust column being 'a major factor in absorbing reaction energy,sufiiciently high inertia of the reaction assembly may be provided ltoaccomplish sufiicient deceleration `and restriction of movement withoutshock absorbers Because the reaction assembly and the impact member areaccelerated in opposite directions, the workpiece 13.2 is impactedbetween the lanvil lili and thrust column while these members are movingin opposite directions, as shown in FGURE 7. The opposing momentumsproduce high impact energy. A large proportion of this energy istransmitted to the workpiece to do useful work in displacing theworkpiece material. The impact energy is transmitted to the workpiece ata very igh rate to produce very rapid displacement.

Some energy is absorbed in decelerating leftward movement of the frame,some is absorbed in the shock absorbers, and a relatively smallproportion of the energy is transmitted to the foot assemblies 12.

After impact, the remaining kinetic energy of the thrust column landpiston carries the frame structure ri glitward, as indicated in FIGURE8. Additional energy is absorbed in accelerating the frame structurerightward `after its leftward movement has been decelerated. Rightwardacceleration is at a relatively low rate. The high inertia of the `framerestricts its acceleration and the shock absorbers 34 exert additionaldecelerating force. Rightward movement of the frame llt) is furtherresisted by the action of cushion plunger ill/l. Movement of the fratriestructure relative to the `actuator housing, as shown in FIGURE 8,`causes the cushion plunger to produce a partial vacuum between thepiston and end wall itl of the housing. The cushion plunger producescompression in chamber 86, seal 116 on the piston providing pressuresealing. The pressure differential between the two sides of the plungerproduces leftward decelerating force on frame structure i0. It is to beunderstood that the cushion plunger H4 is not essential to the operationof the apparatus of the present invention.

After rightward movement of the frame structure and the actuator pistonis decelerated, the frame is urged leftward to its normal centeredposition. The setting pressure in chamber 855 urges the actuator pistonleftward against orifice plate 79, as indicated in FIGURE 9. Thepressures in the sealed pneumatic chambers 56 and 58 of shock absorbers34 exert a centering force on the frame structure. A pressuredifferential between the two charnbers is produced by frame movement offcenter and exerts a centering force which Vassists in repositioning theframe relative to the foundation. The positions of annular pis- 6 tons46 and 48, shown in FIGURE 5, correspond to the centered positions ofthe frame and actuator housing shown in FIGURE 2.

After the cushion plunger 114 contacts end wall 70 during leftwardmovement of the frame, frame structure 1t) may move a limited distancefurther leftward against the resilient urging of springs 126, as shownin FIGURE 9. This movement against the force of the springs serves toabsorb some of the energy of rapid leftward movement of the frame andtherefore reduces shock and stress on the frame structure and on thehousing.

After the components of the apparatus have been repositioned to theconfiguration shown in FIGURES 2 and 9, the machine is ready for repeatoperation.

In order to prepare the actuator for repeat operation, the actuatorpiston must be reseated against the orifice plate to re-establishpressure sealing by means of resilient seal 98. Reseating is preferablyeffected by reducing the ressure in chamber 86 to a value -below thepressure in chamber 83. The latter pressure then moves the piston to theorice plate.

It is important to prevent the trapping of pressure, as circular seal 98contacts the surface of the orifice plate on reseating, in the spacedefined by annular seal it), circular seal 98, the piston, the orificeplate, and cylindrical section 78. Such trapping is prevented, in themanner described in the copending application of Jack Benton Ottestadand Samuel Arthur Skeen, hereinbefore mentioned, by the provision ofexterior fluid connections and a unidirectional check valve (not shown)between orifice plate passages 9) `and 91. Pressure is automaticallyrelieved through the passages, connections, and unidirectional checkvalve into chamber 86. If it were not relieved, trapped prsure would actupon the actuator piston area outside seal 9S and would tend to balancethe force exerted on the opposite side of the piston by the settingpressure. Obviously, the pressure in chamber 86 could not be increasedto the actuating pressure required for sudden release over the piston toeffect rapid piston acceleration. instead, upon increasing the pressurein chamber 86, the piston would be moved and seal 98 would be disengagedby a lower pressure in chamber 86 `acting upon the area within circularseal 98%, because of the force exerted by the trapped pressure.

Although a specific embodiment of the present invention has beendescribed and illustrated in detail, it is to be clearly understood thatthe same is by way of illustration and example only; it is to beunderstood that the invention is not limited thereto, as many variationswill be readily apparent to those versed in the art and the invention isto be given its broadest possi-ble interpretation within the terms ofthe appended claims.

The inventors claim:

1. An impacting apparatus comprising a reaction assembly slidablymounted relative to a foundation, said reaction assembly includingactuator housing means, an actuator piston in the housing means, athrust column connected with the piston, said piston and thrust columnhaving relatively small mass, a plate in the housing confronting the`actuator piston and defining an orifice, sealing means between theactuator piston and the plate for effecting pressure sealingtherebetween about the orifice, means for exerting a setting force tourge said actuator piston toward the plate to cover the orifice andeffect said pressure sealing, and means for establishing an actuatingpressure to act upon a portion of the actuator piston within the sealingmeans to overbalance the setting force and expose an increased area ofthe actuator piston to said actuating pressure to accelerate saidactuator piston and said thrust column, and means on the reactionassembly confronting the thnust column for receiving the impact thereof,the reaction assembly having relatively high inertia to resistacceleration in reaction to the acceleration of the thrust column and toresist deceleration and acceleration in response to said impact, wherebya relatively 7 small proportion yof impact energy is transmitted to saidfoundation.

2. An impacting apparatus comprising a reaction assembly of relativelylarge mass, foundation means slidably supporting the reaction assembly,decelerating means for opposing movement of the reaction assembly, saiddecelerating means including an hydraulic shock absorber connectedbetween said foundation means and said reaction assembly, said shockabsorber having pistons and means defining at least one orifice betweensaid pistons, said pistons 'being carried by said reaction assembly whensaid reaction assembly slides relative to said foundation to producehydraulic resistance to such sliding movement of said reaction assembly,an impact member of relatively small mass slidably positioned in thereaction assembly, means for rapidly accelerating the impact member tohigh velocity relative to the reaction assembly, and means on thereaction assembly for receiving the impact of the impact member, thereaction assembly having relatively large lmass to resist accelerationin reaction to the acceleration of the thrust column and to resistacceleration and deceleration in response to said impact, whereby arelatively small propo-rtion of impact energy is transmitted to thefoundation.

3. An impacting apparatus comprising, a frame structure slidablysupported by a foundation, a housing having opposite ends being slidablycarried by said frame structure, an impact member of relatively lowinertia being movably positioned in said housing, actuator means in saidhousing for accelerating said impact member relative to said housing,means for admitting a pressurized medium into said housing to actuatesaid actuator means, means on said frame structure for receiving theimpact of said impact member, said frame structure and said housingconstituting a reaction assembly having relatively high inertia toresist acceleration in reaction to the acceleration of said impactmember and to resist acceleration and deceleration in response to saidimpact, and a cushion plunger positioned within said housing at one endthereof and attached directly to said frame structure through said oneend of said housing for resisting movement of said frame structureaf-ter said impact by producing a pressure differential on oppositesides of said plunger in said housing, said pressure differential beinglthe differential between the pressure within the space between one sideof said plunger and said one end of said housing and the pressure ofsaid pressurized medium in said housing on the opposite side of saidplunger.

4. A dynamic impacting machine comprising a frame structure having atleast two guide rods, actuator means slidably mounted on at least one ofthe guide rods, foundation means adapted to slidably receive at leastone of the guide rods to support the frame structure, a thrust column ofrelatively low inertia carried by the foundation means and adapted to berapidly accelerated in a first direction by the actuator means, andmeans on the frame structure for receiving the impact of the thrustcolumn, the frame structure and the actuator means constituting areaction assembly of relatively high inertia to resist acceleration in asecond direction in reaction to acceleration of the thrust column and toresist acceleration in said first direction in response to said impactof the thrust column, and an hydraulic shock absorber connected withsaid foundation means and disposed about the guide rod slidably receivedby the foundation means, said shock absorber having piston and meansdefining at least one orifice Ibetween said pistons said pistons beingcarried by said guide rod to cooperate therewith to produce hydraulicresistance to movement of said frame structure, whereby impact energy isprovided with only limited transmission of forces to the foundation.

`5. A dynamic impacting machine comprising a frame structure having atleast two guide rods, foundation means adapted to slidably receive atleast one of the guide rods to support the frame structure, an actuatorhousing slidably mounted on at least one of the guide rods, a platedefining an orifice within the housing, an actuator piston positioned inthe housing, a thrust column connected with the piston and extendingfrom the housing, sealing means between the actuator piston and theplate for effecting pressure sealing therebetween about the orifice,means for exerting a setting force urging said actuator piston towardthe plate to cover said orifice and effect said pressure sealing, meansfor establishing an actuating pressure within said housing means, meansfor releasing the actuating pressure over an area of the actuator pistonto rapidly accelerate the piston and thrust column in a first direction,and means on the frame structure for receiving the impact of the thrustcolumn, the frame structure and the actuator housing having high inertiato resist acceleration in a second direction in reaction to the thrustcolumn acceleration and to resist deceleration and acceleration inresponse to said impact of the thrust column, whereby high impact energyis provided with transmission of only a relatively small porportionthereof to said foundation.

6. A dynamic impacting apparatus comprising a frame structure slidably-supported by a foundation, actuator housing means slidably mounted onthe frame structure, an actuator piston in the housing means, a thrustcolumn connected with the piston, a plate in the housing confronttingthe actuator piston and defining an orifice, sealing means between theactuator piston and the plate for effecting pressure sealingtherebetween about the orifice, means for exerting a setting force tourge said actuator piston toward the plate to cover the orifice andeffect said pressure sealing, and means for establishing au actuatingpressure to act upon a portion of the actuator piston within the sealingmeans to overbalance the setting force, thereby exposing an increasedarea of the actuator piston to said actuating pressure to acceleratesaid actuator piston and said thrust column in a first direction, meanson the frame structure for receiving the impact of the thrust column,said frame structure and said actuator housing having high inertia toresist acceleration in a second direction in reaction to theacceleration of the thrust column and to oppose deceleration andacceleration in response to said impact, and a cushion plunger connectedwith the frame structure and slidable in the actuator housing, saidcushion plunger opposing movement of the frame structure in said firstdirection after said impact by moving relative to said housing toproduce compression on one side of the plunger and a partial vacuum onthe opposite side thereof, whereby high impact energy is provided andonly a relatively small proportion thereof is transmitted to saidfoundation.

7. A dynamic impacting apparatus according to claim 6, `and furtherincluding decelerating means connected with said foundation for opposingmovement of the frame structure relative to the foundation, whereby highimpact energy is provided with transmission to the foundation of onlythose forces developed by the decelerating means.

8. A dynamic impacting machine comprising a frame structure having atleast two guide rods, foundation means adapted to slidably receive atleast one of the guide rods to support the frame structure, an actuatorhousing slidably mounted on at least one of the guide rods, a platedefining an orifice within the housing, an actuator piston positioned inthe housing, a thrust column connected with the piston and extendingfrom the housing, sealing means between the actuator piston yand theplate for effecting pressure sealing therebetween about the orifice,means for exerting a setting force urging said actuator piston towardthe plate to cover said orifice and effect said pressure sealing, meansfor establishing an actuating pressure within said housing means, meansfor releasing the actuating pressure over an area of the actuator pistonto rapidly accelerate the piston .and thrust column in a firstdirection, means on the frame structure for receiving the impact of thethrust column, the frame structure and the actuator housing having highinertia to resist acceleration in a second direction in reaction to thethrust column acceleration and to resist deceleration and accelerationin response to said impact of the thrust column, and an hydraulic shockabsorber connected with said foundation means and disposed about theguide rod slidably received by the foundation means, said shock absorberhaving means defining at least one orifice between pistons carried -bysaid guide rod to cooperate therewith to produce hydraulic resistance tomovement of said frame structure, whereby impact energy is provided withonly the forces developed in the shock absorber being transmitted to thefoundation.

References Cited in the file of this patent UNITED STATES PATENTSNickerson Jan. 15, 1889 Reilly Jan. 10, 1893 Saives May 17, 1938 JohnsonOct. 11, 1938 Fletcher Jan. 1, 1952 FOREIGN PATENTS Great Britain Feb.19, 1937 Great Britain Dec. 12. 1956

